$$\text{a.}\;\;\;y = rcos\theta, z = rsen\theta, x = z$$ $$E = \lbrace (r, \theta, z)|1 \le r \le 3, 0 \le \theta \le 2\pi, 0 \le z \le 1 - r^2\rbrace, f(r, \theta, z) = z$$ $$\text{b.}\;\;\;\int_1^3\int_0^{2\pi}\int_0^{1-r^2} f(r, \theta, z)zrdzd\theta dr = \frac{356\pi}{3}$$